The invention relates to a venting device for an injection mold, in particular for foam molds for steering wheels as well as a method for venting such an injection mold.
If an injection molding material is introduced into the cavity of an injection mold in order to manufacture a formed part, the air being present in the cavity and being replaced by the injection molding material has to be released from the cavity through at least one venting opening of the injection mold via which the cavity communicates with an exterior space surrounding the injection mold. In this connection, there exists the problem that injection molding material escapes out of the venting opening together with the air to be released. This burr has to be removed after the solidification of the injection molding material.
FR 2 857 898 discloses a venting device in which in one venting opening or in several venting openings of the cavity a piston is guided in a venting opening with slackness in each case. Air can exhaust along the piston out of the cavity in a venting position of the piston. To subsequently remove material gotten into the venting opening out of the venting opening, the piston can be moved from the venting position in the direction of the cavity. In this manner, the piston pushes material being present in the venting opening back into the cavity. Possibly, material can stick to the piston itself which material gets then again into the venting opening during an anew movement of the piston into the venting position.
DE 101 53 159 A1 discloses a venting device in which a valve pin is movably guided between two end positions in an opening. In the first end position of the valve pin, air can exhaust from an injection mold to atmosphere through ducts provided in the valve pin. To remove injection molding material possibly being present in the ducts of the valve pin before a further injection molding process, the valve pin can be transferred into a second end position. When the valve pin is moved from its first into its second end position, it is guided past an area of the venting device at which injection molding material being present in the ducts of the valve pin is wiped off. Subsequently, the valve pin is again moved into its first end position for venting the injection mold.